The primary focus of dungeon crawls in the Perilous Halls of Sorrow and Aldsburg campaigns are exploration and loot. Monsters are designed to be obstacles to overcome or avoid rather than wandering bags of experience points. As such, the xp total for creatures in the Hacklopedia are used to build the encounters, but the total amount of xp gained is much smaller - clever players should avoid combat when they can or use other methods to overcome their foes.
As such, I created a series of random encounter tables based on the type of monster encounter (common, uncommon, rarity, paragon, and boss) based on the dungeon level and the expereince points of suggested encounters for those levels. Then, looking at the lists, I really felt like the creatures just didn't fit the tone of the dungeon.
While I've always created creatures specifically for the dungeon and adventures, I've started taking the base monster from the created encounter lists and making changes to help them fit the tone. For example, the creature below was originally based on the giant scorpion. It just didn't feel right in the dungeon, so it became a huge crab covered in mold and fungus.
This is (hopefully) the first of many creatures that will be more fleshed out and compiled into a monster book. The Lusus Naturae book was a huge inspiration - and the HM4e variant creatures book (Matrix? Field Guide?) has suddenly come to mind as well. Stats are for HM5e.
Giant Mold Crab
These dungeon scavengers are mold-covered relatives of the ocean crab. They range in color from rusty red and brown to puke green and yellow all depending on what kind of fungus they are living amongst. The usual giant mold crab is about 60 pounds when fully grown. They are slow moving but still pack some nasty damage with their giant flabby claws.
Tactics are pretty straight forward. Anything moving is a potential meal. Anything not moving but organic (like a corpse or sleeping adventurer) is also a potential meal. The giant mold crab will strike from hiding or attempt to sneak up on the prey.
Once engaged they attack with their mold covered claws to inflict 2d4+3 damage per hit. On a shield hit, they may grab and throw the shield. If the crab flees combat it will retreat as quickly as possible using the Full Parry rules (deflecting blows with their claws).
When found in a nest there will usually (90%) be one female covered in 4d10 fist-sized young mold crabs. If removed from their mother each crab has a 10% chance per hour to simply die off. Living young, however can be sold to alchemists and wizards and weird pet collectors.
Shield Grab - on a shield hit the damage rolled is added to a d20p. The target must pass a Feat of Strength vs. this value or their shield is ripped from their grasp and thrown 2d6p feet away.
Bulwark Shell - DR is considered 6 against blunt weapons, but if the weapon does any damage use the normal DR of 2 to calculate the wound
Hide: 45 in fungal pile or dirty water
Sneak: 20 in natural surroundings
Initiative: +0, Reach 2
Attack: +5, Speed 5, Damage 2d4+3
Defense: +0 (no shield), DR 2*, TOP Save 1-5
Saves: +5 all, +20 poison